In some embodiments, the invention relates to optical 3D scanning of the geometry of body orifices, in particular in-ear scanning and intra-oral scanning. Scanners for this purpose are generally handheld. In particular the parts that enter the body orifice—generally some sort of tip, must fulfill requirements to hygiene and the quality of images taken. Optical signal quality deteriorates when condensation occurs on optical elements such as lenses or filters. The afore-mentioned body orifices have a very humid, warm microclimate, so condensation will likely occur on surfaces that, prior to insertion into the body orifice, were at ambient temperature.
The prior art has several approaches to prevent condensation on the optical elements of intraoral, i.e., dental scanners.
U.S. Pat. No. 7,946,846 (Cadent Ltd) describes a tip with auxiliary nozzles that direct a stream of gas to or from the optical surfaces and the teeth, in particular where the gas is at a temperature above body temperature. A flow of ambient air around exposed tissue can however increase the risk of infections both for the patient and the dentist. An air flow can also cause pain during dental treatment, and discomfort and noise when scanning in the ear canal.
Other manufacturers of intraoral scanners use electrical elements to heat the optical elements exposed to the body orifice. These electrical elements can either be installed inside the scanner (e.g., 3M Lava C.O.S.), or externally, such that heating only occurs when the scanner is at rest outside the body orifice (e.g., Sirona Cerec has a heating element on a cart).
Manufacturers of intraoral scanners have used several approaches to providing hygiene, particularly for those parts entering the body cavity. Some manufacturers provide single-use tips (Cadent iTero). For the 3M Lava C.O.S. scanner, the manufacturer recommends single-use plastic sleeves, which however—because of a need for high image quality—have a hole where the optical elements are located, and hence additional surface sterilization by liquid agents is recommended. For at least one device (Sirona Cerec), hot air sterilization is recommended by the manufacturer. At least one scanner (3Shape TRIOS) has a removable tip that can be steam autoclaved.
Steam autoclaving is considered the safest general-purpose sterilization method, and is accordingly recommended by authorities and standardized (e.g., EN 13060). Consequently, essentially all dental practices have a least one steam autoclave, while hot-air autoclaves are uncommon. The German Federal Institute for the Prevention of Infectious Diseases (Robert Koch Institut, RKI) has published a guideline for hygiene procedures for dental devices based on the German implementation of the Medical Device Directive 93/42/EEC [1]. For instruments used in restorative treatment (like a tip on an intraoral scanner), the guideline prescribes a sequence of cleaning in an instrument washer and steam autoclaving. A similar guideline for the US has been published by the Centers for Disease Control (CDC) [2].
While thus preferable from a hygiene perspective, the combination of an instrument washer and a steam autoclave is harsh on materials and assembly agents such as glues. This is presumably is why apparently only one scanner on the market, 3Shape TRIOS, allows this optimal form of sterilization.